


Cass Jackson and the Lightning Thief

by therearenobananasinthesky



Category: Percy Jackson and the Olympians & Related Fandoms - All Media Types, Percy Jackson and the Olympians - Rick Riordan
Genre: Autistic-Coded Character, Bilingual Character(s), Cabins, Fluff and Angst, Found Family, Genderbending, Hermes Cabin - Freeform, How Do I Tag, I Wrote This Instead of Sleeping, I am very sorry, Ill add more tags as I think of them, Latino Character, Latino Percy, Percy Jackson has a Twin, couldnt be me, eventual lgbtq+ but they're babies for now, i can’t write dialogue, i did this instead of school, i only have grammarly because of my school, i think i use it more for fanfiction than actual school, imagine not using hurt comfort fanfic to deal with trauma, i’m just projecting onto cassie at this point, luke castellan being a good brother, no beta reader we die like men, no editing only grammarly, no romance until the fourth book, the title's uncreative but it's fine, tries to murder percy, until he you know, we love unhealthy coping mechanisms for trauma
Language: English
Status: Completed
Published: 2020-04-28
Updated: 2021-01-27
Packaged: 2021-03-01 21:13:37
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 4
Words: 4,382
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23893624
Author URL: https://archiveofourown.org/users/therearenobananasinthesky/pseuds/therearenobananasinthesky
Summary: When Cassandra “Cass” Jackson was seven years old, she ran away from home. Only halfway through second grade, she had had enough of her new stepfather. As much as she hated leaving her mom and brother, she didn’t feel safe around Gabe and decided to take it into her own hands.~~~basically one of those stereotypical "Percy has a twin" fics where the twin is vaguely self-inserty and kind of OP, but I tried to not be like that. his twin is actually like 10 months older than Percy, but they're close enough the might as well be twins. It's from the perspective of the sister, but she's more of a side character in the main plot, though she has importance to the main characters. I thought it would be interesting to show the quests from the camp's perspective, which was why I chose this.
Relationships: Annabeth Chase & Original Female Character(s), Annabeth Chase & Percy Jackson, Luke Castellan & Annabeth Chase, Luke Castellan & Annabeth Chase & Thalia Grace, Percy Jackson & Grover Underwood, Percy Jackson & Original Female Character(s)
Kudos: 8





	1. Prolouge

When Cassandra “Cass” Jackson was seven years old, she ran away from home. Only halfway through second grade, she had had enough of her new stepfather. As much as she hated leaving her mom and brother, she didn’t feel safe around Gabe and decided to take it into her own hands. It was only two weeks before she found Luke. She probably would have died if he hadn’t found her: she could barely hold her own against the monsters. As they were on the run, Luke would do odd jobs to keep them fed, if anyone thought he looked a bit on the young side to be working, they didn’t question it. Nor did they question how a pale blond kid was the older brother to a tiny Latina. The Mist was plenty helpful for that. 

After five months on the run together, they found Thalia, and then Annabeth. They stuck together until Grover found them and tried to get to camp. They still got stuck in the cyclops’ den in Brooklyn, though Cass, coming from New York, realized their mistake, though not before it was too late. Thalia still sacrificed herself at Half-Blood Hill to save her friends, and Luke is left alone to raise the two girls. Somewhere along the line, Cass is claimed as a daughter of Persephone. As such, Cass and Luke were able to stay together in the same cabin, though Annabeth has to go sleep with her new brothers and sisters. The three can’t help but feel a little bitter that they were so quickly ripped from each other, that they didn’t even have one night together to mourn. 

For five years, they stayed at camp, they trained, and they learned. They learned normal school things, but they also learned Greek and Latin and they learned how to fight. The older Athena kids helped Annabeth to use her skills, and Luke and Cass both learned to use their powers on their own. After two years, Luke became head counselor of Hermes. 

As Cass grew older, she began to grow in her power. As a daughter of Persephone, split between two worlds, so were her powers, split fairly evenly between Underworld powers and those of springtime. As such, she made friends with Katie Gardiner from the Demeter cabin. The Demeter kids helped her grow her skills with plants, though she was on her own in her Underworld powers. 

Four years after she arrived at camp, Grover called in Chiron to see a powerful demigod he had been watching. Chiron ended up spending the whole school year there, only returning for the summer season. What Cass didn’t know was that it was her long-lost brother they were watching over. 

A week after Chiron returned, the whole camp was abuzz about a new kid who defeated the Minotaur on his way in. She figured that it was the same kid that Chiron and Grover had been watching all year, still oblivious to the fact that it was Percy. 

What was most frustrating for her was that Chiron refused to let her see the new kid until he was better. Annabeth was allowed to go in and even feed him ambrosia, so why shouldn’t she be allowed in? It was absolutely unfair, but Chiron said seeing her would “only confuse the boy”, whatever that meant. 

~~~

The Hermes campers were chilling out in the pie cabin for unit time when Annabeth and someone else, probably the new kid, came up to the cabin. A new camper! 

“Regular or undetermined?” Shouted one of the Stolls, probably Conner, and everyone groaned at Annabeth’s answer- no one wanted to welcome a new camper only for them to be taken away.

“Hey, don’t blame the kid,” said Luke, “we take in anyone who doesn’t know their godly parent yet-“

He was cut off by Cass shouting, “or if your parent’s not important enough to get a cabin!”

“So we’re literally the reject cabin!” Finished Travis.

“Anyways,” Luke said with a pointed look at the two, “Hermes, our patron, is the god of travelers, so it makes sense that we take in any unclaimed campers. Anyways, we can probably find you a spot on the floor for your stuff and we’ll give you a sleeping bag.”

As he said that, the new camper stepped in, and Cass saw his face for the first time.

“Percy?”

“Cassie?” He exclaimed, “I thought you were dead!” For the first time in six years, the two half-siblings embraced. “I.. have bad news,” Percy began nervously.

“What is it?”

“Mom… she’s gone, Cassie. She’s dead.” They cried together as they hugged each other, mourning the loss of their mother, and wondering how their life got here.

**Notes for the Chapter:**

> I hope y'all like that! I've kind of had this idea in my head since like seventh grade, but I've been developing it since and I'm finally writing it down. If y'all have like constructive criticism or anything, please let me know in the comments! I hope she doesn't seem to OP, I tried to represent Persephone well.


	2. Percy and Cass at camp

**Notes for the Chapter:**

> nothing annoys me more than when the thing says "chapter 2: chapter 1" because of the existence of a prologue and now I've written a prologue and I have to figure out chapter titles :(

After Annabeth took Percy to finish the tour, Hermes cabin didn’t do much until they had boating at one with the Ares kids. When they got there, they looked furious, and Clarisse was drenched head to toe. “That little punk,” they heard her muttering, “Newbie’s gonna pay on Friday.” Friday was capture the flag. Cass and the Hermes cabin all looked at each other— what could Percy possibly have done to piss off the Ares kids on the first day?

It turned out they didn’t have to do much poking around to find out, because one of the Ares kids was loudly ranting about it as he boarded his canoe. “How the fuck did he even do that? The bathroom just exploded!”

The Hermes kids turned to look at each other, whispering excitedly. Cass was extremely proud of her brother and made sure everybody knew it. 

~~~

After that, they went about on their canoeing lesson as normal, and nothing out of the ordinary happened for a few days. Cabin 11 went to their activities, did their chores, and went to meals just like normal. Percy got settled into daily life at Camp Half-Blood, and Cass spent all her free time with him to make up for the six years they spent apart. When she wasn’t though, she talked to Annabeth about who Percy’s godly parent would be. They knew that it wasn’t the same as Cass’s, Sally had told her that much before she ran away, but they didn’t have any leads. Cass was hoping it was Hermes or another minor god so he could stay with her, but Annabeth was convinced it was one of the Big Three. There was nothing particularly interesting until their next sword-fighting lesson.

Sword-fighting was always interesting for those in the Hermes cabin— Luke was an excellent swordsman and would teach them new maneuvers. Even if they usually couldn’t master the tricks, it was always fun to watch Luke pull them off on whatever poor sap Luke chose to demonstrate on. Today’s lesson, however, was going to be especially interesting, because they had finally mastered the last technique he had shown them, and they were going to move on to a new one.

Cass and some of the other younger campers had guessed that Percy, being the new kid, would be the one Luke would choose to demonstrate on, and they were correct. Cass almost felt sorry for her brother but figured it would still be funny. 

As expected, Luke’s demonstration proved to be hilarious. He got Percy in the ring, built up his confidence, until Luke saw the opening he needed, forcing Percy to drop his sword. By this point, they had both worked up a sweat, so Luke called for a water break. Luke poured water over his head, and Percy copied him. It was kind of cute how Percy immediately tried to do what Luke did— it’s like he was a kitten trying to imitate his mama.

What happened after that, however, shocked everyone involved, including, it seemed, Percy. By some stroke of luck, he managed to overpower Luke and disarm him. Most were too shocked to react, but Cass immediately started cheering for Percy. Once Luke got over the shock of a 12-year-old beating him, he got a spark in his eyes, ready to train and push Percy to his best. Whatever seemed to come over Percy had clearly run out, however, because he couldn’t do it again, no matter how hard Luke pushed him. Cass’s face fell, though she noticed that he still had some talent with his sword, and probably could’ve held his own if he were sparring with anybody but Luke.

~~~

It felt like no time before it was Friday. Cabin 11 had formed an alliance with Athena in exchange for chores. Other things that could be bartered was dessert privileges or the best times in the schedule for certain activities, but the Hermes kids liked chores because they were lazy. Cass helped Beckendorf fit Percy for armor, and found him a sword to use for the game.

When Annabeth told everyone their roles for capture the flag, Cass was suspicious of Percy’s assignment. She may have been no Athena kid, but she knew enough about battle strategy and also about Annabeth to know that it was weird that Percy was assigned on border duty alone. But she didn’t mention it because she knew that if she did ask, Annabeth would just get all cryptic and say something like, “Athena always has a plan.”

Cass was assigned to guard the flag with the Stolls and two Apollo kids. Annabeth liked to keep Cass near the flag because with her powers, she can manipulate the plants to cover up the flag. Of course, she couldn’t just make plants grow out of nothing like some of the Demeter kids on the other side could, but she could get the trees to shift their leaves to block the view of their flag.

Guard duty was unusually quiet this time. Usually, she’d be able to get a few fights in with the Ares kids, they were fun to duel with. But it had been weirdly silent since Luke, Annabeth, and the Apollo counselor had left with their individual scouting groups. It had been maybe half an hour, and not a single Ares kids were to be seen. When the red team eventually did show up, though, it was only a few Demeter and Aphrodite kids. Her group easily fought them off, and before long, they heard the conch horn signaling that the game was over. Considering the fact that their flag was right there with them, they knew that someone had gotten the Ares flag and they started cheering.

They began to run towards the creek, which they would follow to get back to camp, but a large crowd stopped them. Cass got on her tiptoes, attempting to see what was going on, and when she got close enough, she gasped. There was her brother, standing exhausted with a nasty looking gash on his forehead. She tried and failed to push through the crowd to get to her brother. But then Annabeth prompted him to stand in the creek, and as he touched the water, the cut slowly knitted itself together, and he seemed to be reenergized. That must be what last sword practice was about! The only question was how…

She didn’t have to wonder for long, however, because suddenly a sparkling blue trident appeared over his head. Percy was a son of Poseidon! She was excited for him, but also a little annoyed once she realized that meant Annabeth won their bet. Damn, I was really hoping for those 5 drachmas! I was gonna get Connor to sneak in some junk food for me, she thought. Even worse was the realization that that meant Percy would have to move out.

~~~

The next week was absolute torture for Cass. It felt like her brother had been brutally ripped away from her just as she got him back. Even worse was the fact that unlike her and Annabeth, the newly formed Cabin 3 schedule had no blocks in common with Cabin 11. She was especially mad during meals— Percy was right there, alone at table 3, and she couldn’t even join him because of the stupid rule. Who even created that rule anyways she grumbled to herself.

Even worse was when Percy was sent to the Oracle and assigned a quest. And of course, he would choose Grover and Annabeth to come with him, why wouldn’t he? Cass was outraged and a little scared for her friends, but she put on a brave face when she, Chiron, and Luke saw them off at the top of Half-Blood Hill. She stood there with Luke, watching Argus drive off in the camp van, wondering if she would ever see her friends again.

**Notes for the Chapter:**

> This chapter felt a lot longer in Google Docs. Sorry that it's short!


	3. What happens at camp when the gang is on a quest?

It was past midnight the first night without the questing trio when Cass climbed into Luke’s bunk, “Hey,” she whispered, “Are you awake?”

“Yeah, Cassie, what’s up?”

“Can’t sleep.”

“Well, you can stay with me if you want. What’s keeping you up?”

“I’m just scared. What if Annabeth and Percy and Grover don’t come back?”

“I don’t know, kiddo. I’m scared too.”

“I hate this. I hate it so much. It’s only been a day, and I hate it.”

“Yeah, I get that. Was it like this when I was on my quest a few years ago?”

Cass sniffled, “Yeah. Me and Annie were so scared and we could barely talk to each other and when you came back, we all thought you were going to die.”

“Yeah, and I have the scar to prove it,” Luke chuckled darkly.

“And it was so scary, not knowing what was going on with you, and… and what if the same happens to them? What if it’s worse? What if… what if they don’t even survive a day?” She sobbed, “What if they’re dead right now and we don’t even know it because they’re just in the woods, somewhere in New Jersey,” she shuddered at the idea of dying in the Garden State.

“Hey, don’t say that, Cassie. They’re alive, I can feel it,” Luke consoled her. There was a beat of silence. “You’re wearing Thalia’s jacket.”

“Yeah.” The night before they arrived at Camp Half-Blood, Cass had come down with a nasty case of pneumonia. In an attempt to bring her temperature up, Luke and Thalia had given her both of their jackets, and also the one blanket they had between the four of them. Cass was still wearing Thalia’s jacket when they crossed over the boundary line, and now she wears it whenever she’s seeking comfort, no matter how hot it is outside. “I’m just… I’m just scared. Can I stay with you for the night?”

“Of course you can, Cassie. You always can.”

“Thanks, Luke.”

“Of course.” After that, she fell asleep in no time.

~~~

It wasn’t long before the rest of the camp figured out that there was some sort of war brewing. Before, there was no doubt that there was some form of tension in Olympus, but the exact specifics were unknown, not much news made it to camp. A fact which is fine for the summer campers, because it just made summer like a haven from the outside world, but for year-rounders like Cass or Luke? It just felt like they were locked away with no hope for escape, so it was frustrating that something so big on the godly front was being kept from them.

But with Mr. D gone, the rest of camp seemed to realize that there was going to be a civil war and figured it was between Zeus and Poseidon— because honestly, when isn’t it a war between Zeus and Poseidon?

Even worse, for Cass, at least, was that everyone was picking sides. So far, on Zeus’s side were cabins 6, 9, and 4, and on Poseidon’s side were 5, 7, and 10. Castor and Pollux in cabin 12 were undecided, and nobody in cabin 11 could agree on who to back. That seemed to be the problem with being the cabin of extras: it was usually harder to agree on something. The Stolls wanted to support Zeus, and two of the unclaimed campers, Ethan Nakamura and Maya Campbell, wanted to help Poseidon. The rest of the cabin was split pretty evenly, but those four were the most vocal. Cass was leaning towards Poseidon because she didn’t want to fight against her brother, and Luke was weirdly quiet about the whole thing.

Chiron’s solution for the discord within the camp, however, was something nobody could have expected. Sometimes, to get campers to interact with people outside of their cabins, each table at dinner would instead have categories to sit at based on opinions, like favorite color, or month. Today’s theme, however, was favorite movie genre. Cass hadn’t seen many movies, so she just followed Luke to the action-adventure table.

If Chiron had hoped that everyone would start talking about how much they loved that type of movie or which movies they’d recommend in that genre, he was sorely mistaken. Predictably, they barely made 5 minutes into dinner before arguments began to break out over which side of the war everyone should support. Somehow, the debate at their table sprung up from a discussion on Titanic— according to one of the Ares boys, it was ocean propaganda designed to make you hate Poseidon. Cass groaned. The war hadn’t even started yet, and it was already fucking up her perfectly good friendships. Katie wouldn’t even talk to her!

So you can imagine the excitement Cass felt when Luke got an Iris message from Percy while they were on the porch of the Big House one afternoon: Luke was on his break, and Cass was skipping archery to make string bracelets with him.

Cass was focused on her bracelet— she was following a new pattern that she didn’t want to mess up, so she didn’t notice that Luke was on an IM until Annabeth and Grover left the scene. “Percy! Hi! How’s your quest doing?” Cass exclaimed.

“Hey, Cassie. I was just about to tell Luke what’s happening.” Percy began to tell Luke and Cass about those dreams that he was having but was interrupted by Cass.

“Whoa Percy, that’s so weird, Luke’s been having nightmares, too. I wonder if they’re connected somehow?”

Luke suddenly got very flustered. “I, well, I’m just worried about this civil war thing that we’re on the brink of. I keep having nightmares of you guys dying or killing each other.”

Cass nodded sagely, seeing nothing odd or suspicious with Luke’s explanation. “Yeah, that really sucks, this whole impending war thing is bothering me, too. We can’t go 5 minutes without a fight breaking out between cabins! It’s horrible!”

Percy squinted at both of them suspiciously, but before he could question Luke’s response, something beeped on his end; Percy told them they only had a minute left.

“I’m sorry we can’t help from where we are Percy, but there’s something you need to know,” Luke began, “It had to have been Hades who stole the master bolt. He was there at the winter solstice, Cass and I saw him on the field trip to Olympus we took.” 

“But didn’t Chiron say the gods can’t take each other’s magic items directly? Wouldn’t he have needed some sort of half-blood to steal it for him?” asked Percy.

“That’s true, but Hades has the helm of darkness. You’d have to be invisible to sneak in and steal the bolt, and that would make it indirect, he could bypass the ancient laws just by that.”

All three of them were silent, but then Luke spoke again, seemingly realizing the implications of what he said, “Oh, shit, I didn’t mean Annabeth. We’re like a little family, she would never.”

“Besides, she couldn’t have, remember?” Cass cut in, “her hat disappeared the day of the winter solstice. She was so worried that her mom was gonna be mad that she wasted her gift.”

“And then Athena barely acknowledged her,” Luke grumbled, “Look, Percy, are you wearing those shoes I gave you? I’d feel better if they’d helped.”

“Yeah! They’ve, uh, they’ve really helped,” replied Percy.

“That’s good,” the rainbow began to fizzle out, Cass assumed it was from Percy’s end. “Well, take care of yourself. Tell Annabeth I miss her and tell Grover he’ll be better this time. No one will get turned into a tree if he just doesn’t get—” but he was cut off by the rainbow disappearing.

“What the fuck, Luke?” exclaimed Cass once the IM was through, “Why would you bring up Thalia, Percy doesn’t need to know that!”

“Really, Cass? Because the way I see it, Thalia would have survived to get to camp if he didn’t fuck up!”

“You blame Grover? That’s ridiculous, how could it possibly be his fault? If anything, it’s the Council’s fault, why couldn’t they have sent a more experienced protector to help us to camp? Thalia was a daughter of Zeus, for fuck’s sake!”

“Yeah? Well, he could have at least KNOWN WHERE CAMP IS!”

“Well, if you blame bad directions for it, then how is it not my fault too! I grew up in New York, I KNOW it, like the back of my hand, I could have helped.”

“Cassie, you couldn’t have known about the Cyclops den. Besides, how could you say anything about the night Thalia died, you were barely even conscious!”

Cass was silent. “Oh, so you want to go there?” She looked to be on the verge of tears.

But Luke was too riled up to care, “Thalia died for us, all while Grover did nothing! Nothing! But if you want to defend him, then fine!”

“Fine!” Cass ran off; she could barely tell where she was running until she ended up at Zeus’s Fist. Only then did she allow herself to let the tears loose, and she cried herself to sleep.

~~~

When Cass woke up, a few hours had passed, judging by the position of the sun. If she had to guess, she’d say it was probably an hour or two out from sunset. While she was debating whether to head back to camp or stubbornly stay at Zeus’s Fist until they realize she’s gone, some sort of monster suddenly appears.

Fuck, she thought, I forgot the woods are still stocked from the last all-camp. She fumbled for the knife she kept in her back pocket in case of emergencies. Before she could reach it, however, the monster lunged and bit her shoulder. She winced in pain and finally managed to take out her knife. She slashed and stabbed until she managed to get a good enough hit for the monster to disintegrate. With the monster gone and the adrenaline wore off, the pain of her shoulder wound began to overtake her. She could barely do anything but lie on the ground and cry. 

She couldn’t tell how long she lay there, but by the time she heard voices, it was nearly dark. She had to guess that whatever attacked her had some kind of venom because everything looked blurry, and she could barely hear the ever-present cicadas. She vaguely registered a few pairs of feet running into her clearing and someone picking her up. She wasn’t sure what was happening, but whoever was holding her felt familiar, and everything went dark.

~~~

When she woke up again, she was in the infirmary. Luke was in a chair to the side of her bed, looking disheveled and worried. He seemed to be falling asleep but bolted upright when she opened her eyes. “Hey, kiddo, how’re you doing?” Cass groaned. “Ok, ok not good, I get it. Do you remember how you got here?” She shook her head. “Yeah, that makes sense, you were pretty out of it when we found you. At one point you started giggling uncontrollably and sang Baby Shark, but only the verse where you lose an arm.”

Cass looked horrified, “I didn’t!”

“You did,” Luke chuckled. “I just kept hearing ‘lost an arm doo doo doo doo’ over and over again, it would’ve been annoying if I wasn’t so scared.”

“I’m sorry.”

“No, no, Cassie, don’t apologize, it wasn’t your fault! I should really be the one apologizing. I should never have said that shit to you. I am so sorry. You didn’t deserve that.” 

“It’s ok.” 

“No, it really isn’t, Cassie, we thought you were going to die, and the last thing I would have said to you was some dumb argument about Thalia. If you died, it would have been my fault.”

Before she could protest to that, Lee Fletcher, who would often work in the infirmary, walked in to check on her. “Oh, good, you’re awake. You scared us; you were out for four days. I’m just going to replace your bandages, ok? Whatever it was that attacked you, it took a nasty chunk out of your shoulder, and the venom wasn’t helping much, either.”

As Lee took off the bandages, it took all of Cass’s self-control not to gag. As he had mentioned, a chunk of flesh was just simply gone from her arm, but not only that, but the area surrounding the wound was a cacophony of purple and green. When he had finished and left, Cass turned back to Luke. “Have Percy and Annabeth come back from their quest, yet?”

Luke furrowed his brow in confusion. “No, that’s the weird thing. The Solstice deadline is only three days away, and we’ve gotten no contact from them since the IM from Denver. I can only hope they’re okay.” Cass nodded in response. She was finding it harder and harder to stay awake, but a yawn escaped her nevertheless. “You sound tired, Cassie, go back to sleep,” Luke smiled, “I’ll still be here when you wake up.” With that, Cass closed her eyes and allowed sleep to overtake her.

**Notes for the Chapter:**

> Gonna be honest, I have no clue what I'm doing, I had that angsty monster idea at like 3 AM (when all the best angsty ideas come) and decided to write it, I hope y'all liked that!


	4. sorry y'all

hey y'all so i've decided to discontinue this fic I don't really like where it's going especially because the plot doesn't really diverge in my head until titan's curse and it's a pain to attempt to write the filler. i also don't like some of the narrative choices i've made. i might rewrite it later on at some point, but not without intense modulations to the plot and exposition. i hope no one was too attached to this, sorry.


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